Nanotechnology Spotlight

Bioactive glass nanofibers as a next-generation biomaterial

(Nanowerk Spotlight) Bioactive glass is currently regarded as the most biocompatible material in the bone regeneration field because of its bioactivity, osteoconductivity (a scaffold’s ability to support cell attachment and subsequent bone matrix deposition and formation) and even osteoinductivity (a scaffold that encourages osteogenic precursor cells to differentiate into mature bone-forming cells). However, the formulation of bioactive glass has been limited to bulk, crushed powders and micronscale fibers. Now, researchers in South Korea and the UK have for the first time fabricated bioactive glass in nanofibrous form. This material, which shows excellent bioactivity, is likely to open the door to the development of new nano-structured bone regeneration materials for regenerative medicine and tissue engineering.

Materials for biomedical applications have been exploited to augment and regenerate human tissues that have been subjected to damage and diseases. Over the last decade the demands on synthetic biomaterials have increased significantly and considerable effort has been devoted to the area of biomaterials and tissue engineering.

Specifically for hard-tissue applications, such as the regeneration and repair of bones and teeth, several bioactive or bioinert materials have been used clinically. Silica-based bioglasses constitute the essential part of such bioactive materials, having already been utilized in numerous orthopedic and dental applications.

Professor Hae-Won Kim from the Department of Dental Biomaterials at Dankook University in South Korea, explained the benefits of bioglass to Nanowerk: "Most in vivo studies on bioglasses have confirmed their excellent biocompatibility with hard and even soft tissues. This is attributed mainly to their ability to form a bioactive layer at the interface in contact with living tissues, namely the hydroxycarbonate apatite (HCA) layer, which is equivalent to the mineral phase of human hard tissues. Based on extensive research conducted in vitro and in vivo, bioactive glasses are considered as one of the most-promising biomaterials for the 'next generation'."

In a recent paper, Kim and his colleagues from Seoul National University (Prof. Hyoun-Ee Kim) and the UCL Eastman Dental Institute in London/UK (Prof. Jonathan C. Knowles) describe the production of sol–gel-derived bioactive glass as a nanoscale fiber by means of an electrospinning technique. The paper, titled "Production and Potential of Bioactive Glass Nanofibers as a Next-Generation Biomaterial", appeared in the August 2006 edition of Advanced Functional Materials.

Bone-marrow derived osteoblastic cell responses to the bioactive glass nanofiber: Electron microscopy images of the cells on the nanofibrous mesh at low (a) and high (b) magnification with 5 days of culturing. (Reprinted with permission from Wiley)

"Applications of the bioactive glass nanofiber include cell matrices for bone regeneration and tissue engineering" says Kim. "The nanofibrous mesh can be used either directly for bone fillers or in composite form with biodegradable polymers such as collagen and polylactic acid."

Nanofibers fabricated through electrospinning are very attractive in the field of biomaterials and tissue engineering because they are mimicking the structure of extracellular matrix of tissue and thus the cells recognize the nanoscale fibrous structure very differently from the conventional substrate.

Kim notes that most research in this field has been focused on polymeric nanofibers either of natural or synthetic base.

"The biomaterials with excellent bone forming ability such as bioactive glass should be considered as a first choice to gain optimal bone regeneration performance" he says. "Therefore, our work is considered to be the first step in generating nano-structured bioactive materials, particularly bioactive glass, in a nanofiber form and is expected to trigger future research to be directed towards this field."

Kim and his colleagues are currently undertaking further research on this bioactive glass nanofiber system, such as explaining the effective role of nanoscale fibrous structure on the cellular behavior and bone regeneration process.